Effect of thermal treatment on microstructure and corrosion behaviour of 316L stainless steel manufactured by selective laser melting

摘要

This work investigates the electrochemical behaviour of an AISI 316L stainless steel produced byselective laser melting (SLM) and compares its behaviour with that of a wrought stainless steelwith similar chemical composition. In particular, the focus of the work is on the effect of thermaltreatments (stress relief and recrystallization annealing) that are typically performed on SLMcomponents. The microstructure of the specimens is investigated by scanning electronmicroscopy and atomic force microscopy. The oxide film on the specimens is investigated by glowdischarge optical emission spectroscopy and by scanning Kelvin probe force microscopy. Thecorrosion behaviour of the SLM specimens is investigated by electrochemical methods(potentiodynamic polarization and electrochemical impedance spectroscopy).At the macro-scale, the microstructure of the SLM specimens is determined by the laser scanningpattern and displays an overlapping network of melt pools. At the micro-scale, the SLM specimensexhibit a cellular/columnar dendritic structure with sub-micrometric cell size. The structure of SLMspecimens is affected by thermal treatment and displays a progressive evolution towards thetypical austenitic structure of the wrought counterpart increasing the temperature of the thermaltreatment. This evolution of the microstructure can be associated to a decrease of the protectiveproperties of the oxide film on SLM specimens.